This invention relates to an arrangement for reducing noise of a machine with a hopper (for crushing, chipping, cutting), or more particularly to a soundproof hopper. In present time hoppers that have to be made from steel sheets radiate more noise than the machine itself, which makes the use of total enclosures widespread. Total enclosures make the machine immobile and associated with a loss of visibility, accessibility and increase in production cost. Although these total enclosures reduce the overall noise of the machine, the worker which loads the machine works in the noisiest place, because the vibrating neck of the hopper radiates noise near and through its opening. The doors of these hoppers have to open to the inside to let the material being loaded through. However, under negative pressure inside the hopper of the working machine these doors open and radiate even more noise.
The use of foam material as a support and vibration isolator as well as an acoustic seal does not prevent noise from leaking through boundary cracks because sound absorbtive foam is not a noise barrier, although it is mistakingly used as such. Another disadvantage of foam material is that with time it shrinks under weight.